Would like client as well as provider perspectives on this one.  

If I see a provider I know fairly well out and about in the city we both frequent as our home turf, do I say hi if it looks like we're both alone?  Or is it best to just avoid outside contact altogether?    

I obviously don't want to be rude to her, especially if she's a regular. But, I guess you never know who might be with each other, or if she's OTC in real life or not. Same goes in the opposite direction. Should the lady avoid making contact with me at all costs, even if it's clear I'm on my own